Image sensor and method of manufacturing the same

ABSTRACT

An image sensor and a method of manufacturing the same. The image sensor includes a plurality of photoelectric conversion units that are horizontally arranged and selectively emit electric signals by absorbing color beams.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of and claims priority under 35 U.S.C.§§120/121 to U.S. patent application Ser. No. 13/234,702, filed on Sep.16, 2011, which claims priority under 35 U.S.C. §119 to Korean PatentApplication No. 10-2011-0002869, filed on Jan. 11, 2011, in the KoreanIntellectual Property Office (KIPO), the entire contents of each ofwhich are incorporated herein by reference in their entirety.

BACKGROUND

1. Field

The present disclosure relates to image sensors and methods ofmanufacturing the same.

2. Description of the Related Art

Image sensors, which are semiconductor devices for converting an opticalimage into an electric signal, may be classified into charge-coupleddevice (CCD) image sensors and complementary metal oxide silicon (CMOS)image sensors. Image sensors include a light-sensing unit for sensinglight, and a logic circuit unit for processing the sensed light into anelectric signal to store data. A logic circuit unit of a CMOS imagesensor using CMOS technology includes MOS transistors disposed on asemiconductor substrate to correspond to unit pixels, and the MOStransistors sequentially detect outputs of the unit pixels in aswitching mode.

Image sensors may include a color filter and a photoelectric conversionfilm. The color filter separates light according to colors, and thephotoelectric conversion film converts light into an electric signal. Assuch, since the color filter and the photoelectric conversion film areseparated from each other, processes for manufacturing an image sensorare complex and since light passes through a plurality of layers, lightutilization efficiency is reduced.

SUMMARY

Provided are image sensors having simple structures.

Provided are methods of manufacturing image sensors having simplestructures.

Additional aspects will be set forth in part in the description whichfollows and, in part, will be apparent from the description, or may belearned by practice of the presented embodiments.

According to an aspect of the present invention, an image sensorincludes: a substrate; first electrodes disposed on the substrate; aphotoelectric conversion layer including a plurality of photoelectricconversion units each of which is horizontally arranged on the firstelectrodes and configured to emit electric signals by absorbingpredetermined or reference color beams of a corresponding color; and asecond electrode disposed on the photoelectric conversion layer.

Each of the plurality of photoelectric conversion units may include ap/n hetero junction layer, p/i/n hetero junction layer, or p/n bulkhetero junction layer.

The photoelectric conversion layer may include a first photoelectricconversion unit configured to emit an electric signal by absorbing ablue beam, a second photoelectric conversion unit configured to emit anelectric signal by absorbing a green beam, and a third photoelectricconversion unit configured to emit an electric signal by absorbing a redbeam.

At least one of the photoelectric conversion units may include a p-typematerial formed of rubrene or a thiophene derivative, and an n-typematerial formed of fullerene or a fullerene derivative.

At least one of the photoelectric conversion units may include a p-typematerial formed of a 3,4-ethylenedioxythiophene (EDOT) derivative, andan n-type material formed of Alq3, naphthalence-1,4,5,8-tetracarboxylicdianhydride (NTCDA), or a C60 derivative.

At least one of the photoelectric conversion units may include a p-typematerial formed of phtalocyanine, and an n-type material formed ofNTCDA, Alq3, or a C60 derivative.

The photoelectric conversion layer may include a patternable material.

Each of the photoelectric conversion layer may include a patternablefunctional group.

The image sensor may further include signal charge readout circuitsconfigured to read out electric signals from the first electrodes.

The image sensor may further include carrier paths connected between thefirst electrodes and the signal charge readout circuits.

According to another aspect of the present invention, a method ofmanufacturing an image sensor includes: forming first electrodes on asubstrate; coating a patternable first photoelectric conversion materialon the first electrodes; patterning a first photoelectric conversionunit and forming a resultant structure by exposing the firstphotoelectric conversion material using a first mask; coating apatternable second photoelectric conversion material on the resultantstructure including the first photoelectric conversion unit; patterninga second photoelectric conversion unit by exposing the secondphotoelectric conversion material by using a second mask; and stacking asecond electrode on the first photoelectric conversion unit and thesecond photoelectric conversion unit.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of example embodiments willbecome more apparent by describing in detail example embodiments withreference to the attached drawings. The accompanying drawings areintended to depict example embodiments and should not be interpreted tolimit the intended scope of the claims. The accompanying drawings arenot to be considered as drawn to scale unless explicitly noted.

FIG. 1 is a cross-sectional view of an image sensor according to anembodiment of the present invention;

FIG. 2 is a partial cross-sectional view of an image sensor according toanother embodiment of the present invention;

FIG. 3 is a partial cross-sectional view of an image sensor according toanother embodiment of the present invention;

FIGS. 4A through 4L illustrate a method of manufacturing an imagesensor, according to an embodiment of the present invention; and

FIG. 5 illustrates an example where a functional group is combined witha photoelectric conversion material used in the method of FIGS. 4Athrough 4L.

DETAILED DESCRIPTION

Detailed example embodiments are disclosed herein. However, specificstructural and functional details disclosed herein are merelyrepresentative for purposes of describing example embodiments. Exampleembodiments may, however, be embodied in many alternate forms and shouldnot be construed as limited to only the embodiments set forth herein.

Accordingly, while example embodiments are capable of variousmodifications and alternative forms, embodiments thereof are shown byway of example in the drawings and will herein be described in detail.It should be understood, however, that there is no intent to limitexample embodiments to the particular forms disclosed, but to thecontrary, example embodiments are to cover all modifications,equivalents, and alternatives falling within the scope of exampleembodiments. Like numbers refer to like elements throughout thedescription of the figures.

It will be understood that, although the terms first, second, etc. maybe used herein to describe various elements, these elements should notbe limited by these terms. These terms are only used to distinguish oneelement from another. For example, a first element could be termed asecond element, and, similarly, a second element could be termed a firstelement, without departing from the scope of example embodiments. Asused herein, the term “and/or” includes any and all combinations of oneor more of the associated listed items.

It will be understood that when an element is referred to as being“connected” or “coupled” to another element, it may be directlyconnected or coupled to the other element or intervening elements may bepresent. In contrast, when an element is referred to as being “directlyconnected” or “directly coupled” to another element, there are nointervening elements present. Other words used to describe therelationship between elements should be interpreted in a like fashion(e.g., “between” versus “directly between”, “adjacent” versus “directlyadjacent”, etc.).

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of exampleembodiments. As used herein, the singular forms “a”, “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises”, “comprising,”, “includes” and/or “including”, when usedherein, specify the presence of stated features, integers, steps,operations, elements, and/or components, but do not preclude thepresence or addition of one or more other features, integers, steps,operations, elements, components, and/or groups thereof.

It should also be noted that in some alternative implementations, thefunctions/acts noted may occur out of the order noted in the figures.For example, two figures shown in succession may in fact be executedsubstantially concurrently or may sometimes be executed in the reverseorder, depending upon the functionality/acts involved.

FIG. 1 is a cross-sectional view of an image sensor 1 according to anembodiment of the present invention. The image sensor 1 includes asubstrate 10, first electrodes 20, a second electrode 40, and aphotoelectric conversion layer 30 that is disposed between the firstelectrodes 20 and the second electrode 40. The substrate 10 may be asemiconductor substrate. The first electrodes 20 may be anodes (orcathodes), and may be used as pixel electrodes. The plurality of firstelectrodes 20 may be horizontally arranged in parallel to the substrate10 to be separated from one another. Each of the first electrodes 20 maybe formed of a transparent conductive material such as indium tin oxide(ITO), indium zinc oxide (IZO), zinc oxide (ZnO), or SnO₂. The secondelectrode 40 may be a cathode (or an anode). The second electrode 40 maybe used as a common electrode. The second electrode 40 may have a workfunction that is less than, equal to, or greater than that of the firstelectrodes 20. The second electrode 40 may be formed of a transparentconductive material such as ITO, IZO, ZnO, or SnO₂, or a metal. Themetal may be at least one selected from the group consisting of aluminum(Al), copper (Cu), titanium (Ti), gold (Au), platinum (Pt), silver (Ag),and chromium (Cr). However, the present embodiment is not limitedthereto. If the second electrode 40 is a metal electrode, the secondelectrode 40 may be a semitransparent electrode with a thickness equalto or less than 20 nm.

The photoelectric conversion layer 30 may convert light into an electricsignal by using a photoelectric conversion effect. Also, thephotoelectric conversion layer 30 may be a color selective layer. Thephotoelectric conversion layer 30 may include a plurality ofphotoelectric conversion units each of which converts a predetermined orreference color beam into an electric signal. The photoelectricconversion units may be respectively disposed in units of pixels. Theplurality of photoelectric conversion units in the photoelectricconversion layer 30 may be horizontally arranged in parallel to thesubstrate 10. For example, the photoelectric conversion layer 30 mayinclude a plurality of photoelectric conversion units that arehorizontally arranged in parallel to the substrate 10 and convertdifferent color beams into electric signals. However, the presentembodiment is not limited thereto, and the photoelectric conversionunits may be arranged in various ways. The photoelectric conversionlayer 30 may include a first photoelectric conversion unit 31 thatabsorbs a first color beam and generates an electric signal, a secondphotoelectric conversion unit 32 that absorbs a second color beam andgenerates an electric signal, and a third photoelectric conversion unit33 that absorbs a third color beam and generates an electric signal.

Each of the first photoelectric conversion unit 31, the secondphotoelectric conversion unit 32, and the third photoelectric conversionunit 33 may have a p/n, p/i/n, or p/n bulk hetero junction structure.Each of the first photoelectric conversion unit 31, the secondphotoelectric conversion unit 32, and the third photoelectric conversionunit 33 may include a p-type material and an n-type material.

The first photoelectric conversion unit 31 may generate an electricsignal by absorbing, for example, a blue beam. The first photoelectricconversion unit 31 may include rubrene as a p-type material, andfullerene or a fullerene derivative as an n-type material. Here, thefullerene may be, for example, C60 fullerene. Additional examples of thefullerene derivative which may be used for the n-type material mayinclude C70 fullerene, C76 fullerene, C78 fullerene, and C80 fullerene.

As another example, the first photoelectric conversion unit 31 mayinclude tetracene as a p-type material, andnaphthalence-1,4,5,8-tetracarboxylic dianhydride (NTCDA) as an n-typematerial. Besides the materials mentioned above, a thiophene derivativemay be used.

The second photoelectric conversion unit 32 may generate an electricsignal by absorbing, for example, a green beam. The second photoelectricconversion unit 33 may include a 3,4-ethylenedioxythiophene (EDOT)derivative as a p-type material. Here, the EDOT derivative may be, forexample, hexa-3,4-ethylenedioxythiophene.

hexa-3,4-ethylenedioxythiophene

The EDOT derivative, e.g., hexa-3,4-ethylenedioxythiophene, may absorb agreen beam. The second photoelectric conversion unit 33 may include Alq3or NTCDA as an n-type material. Besides, a cyanine-based pigment or asquarylium-based pigment may be used as a p-type material. Also, Alq3 orC60 may be used as an n-type material.

The third photoelectric conversion unit 33 may generate an electricsignal by absorbing, for example, a red beam. The third photoelectricconversion unit 33 may include NTCDA, Alq3, or C60 as an n-typematerial. And, the third photoelectric conversion unit 33 may includephtalocyanine as a p-type material.

Although one first photoelectric conversion unit 31, one secondphotoelectric conversion unit 32, and one third photoelectric conversionunit 33 are arranged in FIG. 1, the present embodiment is not limitedthereto, and one first photoelectric conversion unit 31, two secondphotoelectric conversion units 32, and one third photoelectricconversion unit 33 may be arranged. Also, the first through thirdphotoelectric conversion units 31, 32, and 33, which are horizontallyarranged in parallel to the substrate 10, may not be aligned but may bearranged in a 2×2 configuration.

Each of the first through third photoelectric conversion units 31, 32,and 33 may be formed of an organic photoelectric conversion material.And, each of the first through third photoelectric conversion units 31,32, and 33 may be formed of a photoelectric conversion materialincluding a patternable material. Examples of the patternable materialmay include, for example, an epoxy group and an acryl group.Alternatively, each of the first through third photoelectric conversionunits 31, 32, and 33 may be formed of a photoelectric conversionmaterial including a patternable functional group. Alternatively, aphotoelectric conversion material may be included as a component inpatternable materials.

Meanwhile, a plurality of signal charge readout circuits 13 may bedisposed in the substrate 10. The plurality of signal charge readoutcircuits 13 may be arranged to be separated from one another. The signalcharge readout circuits 13 may be disposed to correspond to pixels ofthe image sensor 1. Carrier paths 15 may be connected between the signalcharge readout circuits 13 and the first electrodes 20. A firstinsulating layer 18 may be disposed between the substrate 10 and thephotoelectric conversion layer 30. Also, a protective film 50 may befurther disposed on the second electrode 40. Alternatively, a micro lensmay be further disposed in order to improve light utilizationefficiency.

An operation of the image sensor 1 will be explained below. When light Lis incident on the image sensor 1, each of beams may be selected forevery pixel by the photoelectric conversion layer 30 to be convertedinto an electric signal. For example, the first photoelectric conversionunit 31 may absorb the energy of a blue beam of the light L incident onthe image sensor 1 to generate electrons and holes, and, for example,the electrons may be moved to the first electrodes 20 and the holes maybe moved to the second electrode 40, thereby enabling current to flowand generating an electric signal. Alternatively, according to a type ofthe photoelectric conversion layer 30, electrons may be moved to thesecond electrode 40 and holes may be moved to the first electrodes 20,thereby enabling current to flow. The second photoelectric conversionunit 32 may absorb the energy of a green beam of the light L incident onthe image sensor 1 to generate electrons and holes, thereby generatingan electric signal. The third photoelectric conversion unit 33 mayabsorb the energy of a red beam of the light L incident on the imagesensor L to generate electrons and holes, thereby generating an electricsignal. The electrons generated in the first through third photoelectricconversion units 31, 32, and 33 may be respectively moved to the signalcharge readout circuits 13 through the carrier paths 15, and may beprocessed as image signals by the signal charge readout circuits 13.

Since the image sensor 1 includes the photoelectric conversion layer 30that is able to select a color, an additional color filter is notnecessary. Accordingly, the number of components may be reduced and thusmanufacturing costs may be reduced. Also, since the photoelectricconversion layer 30, which is able to select a color, is horizontallyarranged, a structure of the photoelectric conversion layer 30 issimple. Also, since the structure of the photoelectric conversion layer30 is simple, a decrease in light utilization efficiency which may occurwhen light passes through a plurality of layers may be avoided.

FIG. 2 is a partial cross-sectional view of an image sensor in onepixel, according to another embodiment of the present invention. Whencompared with the image sensor of FIG. 1, there is a difference in astructure between a first electrode 120 and a second electrode 140. Aphotoelectric conversion layer 130 may be disposed between the firstelectrode 120 and the second electrode 140, and a first buffer layer 125may be further disposed between the first electrode 120 and thephotoelectric conversion layer 130.

FIG. 3 is a partial cross-sectional view of an image sensor according toanother embodiment of the present invention. Referring to FIG. 3, asecond buffer layer 135 is further disposed between the photoelectricconversion layer 130 and the second electrode 140. Alternatively, thefirst buffer layer 125 may be disposed between the first electrode 120and the photoelectric conversion layer 130, and the second buffer layermay be disposed between the photoelectric conversion layer 130 and thesecond electrode 140.

The first and second buffer layers 125 and 135 may be used as electrontransport layers in order to more easily carry electrons. Alternatively,the first and second buffer layers 125 and 135 may be used as holeblocking layers. The hole blocking layers may act as protective filmsfor preventing the migration of holes and preventing electricalshort-circuit. Alternatively, the first and second buffer layers 125 and135 may function as both electron transport layers and hole blockinglayers. The first buffer layer 125 may include, for example,poly(3,4-ethylenedioxythiophene) (PEDOT) or poly(styrene sulfonate)(PSS). The second buffer layer 135 may bathocuproine (BCP) or LiF.

FIGS. 4A through 4L are cross-sectional views illustrating a method ofmanufacturing an image sensor, according to an embodiment of the presentinvention.

Referring to FIG. 4A, a plurality of signal charge readout circuits 213may be formed by using a semiconductor process in a substrate 210. Thesignal charger readout circuits 213 may be formed to have the same topsurfaces as a top surface of the substrate 210. The signal chargereadout circuits 213 may be horizontally arranged in parallel to thesubstrate 210 to be separated from one another. Referring to FIG. 4B, afirst insulating layer 218 is stacked on the signal charge readoutcircuits 213. Referring to FIG. 4C, via-holes may be formed by using wetetching or dry etching in the first insulating layer 218, and thevia-holes may be metalized to form carrier paths 215.

Referring to FIG. 4D, a first electrode layer 219 may be coated on aresultant structure illustrated in FIG. 4C, and referring to FIG. 4E, aplurality of first electrodes 220 may be formed by using, for example,photolithography. Next, referring to FIG. 4F, a first photoelectricconversion layer 231 may be coated on the first electrodes 220. Thefirst photoelectric conversion layer 231 may include a material whichcontains a patternable material and undergoes photoelectric conversionwith respect to a first color beam. The first photoelectric conversionlayer 231 may include a material that contains a patternable functionalgroup and undergoes photoelectric conversion with respect to a firstcolor beam. The material that undergoes photoelectric conversion withrespect to the first color beam, for example, a blue beam, may includerubrene as a p-type material, and may include fullerene or a fullerenederivative as an n-type material. FIG. 5 illustrates a structure inwhich a patternable functional group R (the functional group may beoxirane, oxetane, vinyl, trifluorovinyl ether, styrene, acrylic,benzocyclobutane, etc) is combined with a photoelectric conversionmaterial. The patternable functional group may be inherently included inthe photoelectric conversion material or may be included as a part ofcomponents.

The first photoelectric conversion layer 213 may be coated by using, forexample, spin coating. Since the first photoelectric conversion layer213 is patternable, the first photoelectric conversion layer 213 may bepatterned by being exposed by using a first mask 235. A firstphotoelectric conversion unit 231 a may be formed by removing a portionof the first photoelectric conversion layer 231 according to a patternof the first photoelectric conversion layer 231. The first mask 235 mayexpose an area where the first photoelectric conversion unit 231 a is tobe formed, or an area other than the area where the first photoelectricconversion unit 231 a is to be formed.

Next, referring to FIG. 4H, a second photoelectric conversion layer 232may be coated on a resultant structure illustrated in FIG. 4G by using,for example, spin coating. The second photoelectric conversion layer 232may include a material that contains a patternable material andundergoes photoelectric conversion with respect to a second color beam.Alternatively, the second photoelectric conversion layer 232 may includea material that contains a patternable functional group and undergoesphotoelectric conversion with respect to a second color beam. Thematerial which undergoes photoelectric conversion with respect to thesecond color beam, for example, a green beam, may include EDOT as ap-type material, and Alq3 or NTCDA as an n-type material. And, thesecond photoelectric conversion layer 232 may be patterned by using asecond mask 236. Referring to FIG. 4I, a second photoelectric conversionunit 232 a may be formed by removing a portion of the secondphotoelectric conversion layer 232 according to a pattern of the secondphotoelectric conversion layer 232.

Next, referring to FIG. 4J, a third photoelectric conversion layer 233may be coated on a resultant structure illustrated in FIG. 4I by using,for example, spin coating. The third photoelectric conversion layer 233may include a material that contains a patternable material andundergoes photoelectric conversion with respect to a third color beam.Alternatively, the third photoelectric conversion layer 233 may includea material that contains a patternable functional group and undergoesphotoelectric conversion with respect to a third color beam. Thematerial that undergoes photoelectric conversion with respect to thethird color beam, for example, a red beam, may include NTCDA as ann-type material, and phtalocyanine as a p-type material. And, the thirdphotoelectric conversion layer 233 may be patterned by being exposed byusing a third mask 237. Referring to FIG. 4K, a third photoelectricconversion unit 233 a may be formed by removing a portion of the thirdphotoelectric conversion layer 233 according to a pattern of the thirdphotoelectric conversion layer 233.

Next, referring to FIG. 4L, a second electrode 240 and a protective film250 may be stacked on the first through third photoelectric conversionunits 231 a, 232 a, and 233 a. Alternatively, a micro lens may befurther disposed on the second electrode 240.

As described above, according to the one or more embodiments of thepresent invention, the method of manufacturing the image sensor maypattern a photoelectric conversion layer that undergoes photoelectricconversion with respect to a predetermined or reference color beam.Since the photoelectric conversion layer is formed by using patterning,a manufacturing process may be simplified, and photoelectric conversionunits of the photoelectric conversion layer may be horizontally arrangedin parallel to a substrate. Since the photoelectric conversion layer isa color selective layer, an additional color filter is not necessary,thereby making it possible to omit a process of manufacturing a colorfilter. It should be understood, however, that there is no intent tolimit exemplary embodiments to the particular forms disclosed, but onthe contrary, exemplary embodiments are to cover all modifications,equivalents, and alternatives falling within the scope of the invention.Therefore, the scope of the invention is defined not by the detaileddescription of the invention but by the appended claims, and alldifferences within the scope will be construed as being included in thepresent invention.

Example embodiments having thus been described, it will be obvious thatthe same may be varied in many ways. Such variations are not to beregarded as a departure from the intended spirit and scope of exampleembodiments, and all such modifications as would be obvious to oneskilled in the art are intended to be included within the scope of thefollowing claims.

What is claimed is:
 1. An image sensor comprising: a substrate; firstelectrodes disposed on the substrate; a photoelectric conversion layerincluding a plurality of photoelectric conversion units, each of theplurality of photoelectric conversion units being arranged on adifferent one of the first electrodes, the plurality of photoelectricconversion units including at least a first photo electric conversionunit and a second photo electric conversion unit, the first photoelectric conversion unit including a first material configured to emitelectric signals by selectively absorbing light of a first color withouta color filter, the second photo electric conversion unit including asecond material configured to emit electric signals by selectivelyabsorbing light of a second color without a color filter, the first andsecond colors being different colors; and a second electrode disposed onthe photoelectric conversion layer, wherein the plurality ofphotoelectric conversion units surround side surfaces of each of thefirst electrodes such that each of the first electrodes are separatedfrom each other, the second electrode including at least onecontinuously planar portion that completely overlaps at least two of theplurality of photoelectric conversion units.
 2. The image sensor ofclaim 1, wherein each of the plurality of photoelectric conversion unitsincludes a p/n, p/i/n, or p/n bulk hetero junction layer.
 3. The imagesensor of claim 1, wherein, the first photoelectric conversion unit isconfigured to emit an electric signal by absorbing a blue beam, thesecond photoelectric conversion unit is configured to emit an electricsignal by absorbing a green beam, and the photoelectric conversion layerfurther includes a third photoelectric conversion unit configured toemit an electric signal by absorbing a red beam.
 4. The image sensor ofclaim 1, wherein at least one of the photoelectric conversion unitsincludes a p-type material formed of rubrene or a thiophene derivative,and an n-type material formed of fullerene or a fullerene derivative. 5.The image sensor of claim 1, wherein at least one of the photoelectricconversion units includes a p-type material formed of a3,4-ethylenedioxythiophene (EDOT) derivative, and an n-type materialformed of Alq3, naphthalence-1,4,5,8-tetracarboxylic dianhydride(NTCDA), or a C60 derivative.
 6. The image sensor of claim 1, wherein atleast one of the photoelectric conversion units includes a p-typematerial formed of phtalocyanine, and an n-type material formed ofNTCDA, Alq3, or a C60 derivative.
 7. The image sensor of claim 1,wherein the photoelectric conversion layer includes a patternablematerial.
 8. The image sensor of claim 1, wherein the photoelectricconversion layer includes a patternable functional group.
 9. The imagesensor of claim 1, further comprising: signal charge readout circuitsconfigured to read out electric signals from the first electrodes. 10.The image sensor of claim 9, further comprising: carrier paths connectedbetween the first electrodes and the signal charge readout circuits. 11.The image sensor of claim 1, wherein the first electrodes are pixelelectrodes and the second electrode is common electrode.
 12. The imagesensor of claim 1, wherein the plurality of photoelectric conversionunits are arranged to contact each other such that the first material isadjacent to the second material.